If the pompino has a drilled fork crown, you can also use one of these;
http://www.dotbike.com/p/6181 (crown mounted brake hanger) - less prone to judder, and better cable routing (ime) than stem/spacer mounted hangers.
Don't forget, YOU NEED TO CHANGE YOUR LEVERS. Unless you have "Mini V" brakes (arm lengths between 85 & 95mm) the levers you have on your bike are designed for V brakes (assuming the spec on On One's website is right, they're Dia Compe 287V, which will not work well with other sorts of brake).
On the brakes - you can get an awful lot of power (probably more than you can from wide profile) from the low profile "shorty" type brake. The downside is that they drift out of adjustment quickly, and the more power you want, the closer they have to be to the rim to stop the lever bottoming out on your bars.
On my bike (with Tiagra road levers) the key to getting low profile brakes to work is to junk the included link wire, and use an old fashioned straddle - the ones Tektro use for the CR720 are particularly good, and are available as an aftermarket part on their own. Set the straddle low - again, on my bike, the clamp bolt is level with the lower headset cup. This puts a LOT of mechanical advantage at the lever - because of this, you need to gap the brakes close to your rims. An inflated tyre won't go past my brakes, and the gap doesn't allow the unhooking of the straddle.
For the CR720s, just set the straddle as low as you can. These are nice brakes, but can be a bit hair raising when braking conditions are less than optimal. With my levers, I tend to brake from drops rather than hoods, and they work ok then. If you're braking from the hoods, grab a LOT of lever and pull hard! They may well work better with levers designed for canti brakes though. These don't use up pads as quickly as the Oryx did, and can be gapped further from the rim. Their mechanical advantage actually increases as the pad approaches the rim too, which is nice. You can also do wheel changes without unclamping the straddle or deflating the tyres.
Whatever brakes you get, junk the included pads and use Koolstop Salmon, Fibrax Xtreme, or BBB tristops.